1. Field of the Invention
The present invention relates to a combined device for power generation and illumination mounted on the wheel axle of a bicycle, and more particularly to a combined power generation and light device mounted onto an external side of a bicycle wheel axle, totally different from the traditional way of generating power by frictions produced between a hub and a tire of the bicycle.
2. Description of the Related Art
At present, there are various types of self power generation lamps used by bicycles and described as follows:
The first type is generally known as dynamo powered lamps as shown in FIG. 1, wherein a small sized power generator 11 is installed at a fork 14 of a bicycle, and a clutch 13 is used for separating the power generator 11 from a tire 15 when the lamp is not in use, and attaching a driving wheel 12 of an axle of the power generator 11 with the tire 15 if light is needed, such that rotation of the tire 15 drives the power generator to rotate, and an electromagnetic conversion process drives the power generator 11 to generate electric power and supply a power source to the bike lamp 16. However, such power generator rubbing the tire comes with the advantages of a simple structure, a low price, and an easy installation, but it still has the following shortcomings:
1. Low Efficiency: Since a single-phase power generator is adopted, the efficiency of the power generator 11 is very low, and the power generator 11 definitely requires a very high rotation speed to supply the electric power required for lighting up the bike lamp 16.
2. High failure rate: Since a high rotation speed is required, the driving wheel 12 is rotated at a very high rotation speed. However, the power generator 11 of that model does not come with a corresponding bearing for the high rotation speed, and thus incurs a high failure rate.
3. Large resistance: The power generator 11 of this model generate power by rubbing the power generator driving wheel 12 with a surface of the tire 15. To assure the contact between the power generator driving wheel 12 and the tire 15, the design of a stronger clutch 13 is provided for the tire 15 to drive the power generator 11 to rotate, so that the pressure of the power generator driving wheel 12 exerted upon the surface of the tire 15 is converted into a resistance, and bicycle rider can feel the large resistance and the hardship of riding the bike.
4. Exposure of electric wire: The bike lamp is not installed directly, and thus a segment of the electric wire 17 is exposed to connect the bike lamp 16, and the electric wire 17 may be pulled apart or deteriorated to cause a short circuit or a break of the electric wire.
The second type is a hub power generator as shown in FIG. 2, wherein the power generator 19 is combined with the hub 18, and a magnet 191 is fixed on an internal side of the hub housing 181, and both ends of a wheel shaft 182 are protruded from the hub housing 181 and mounted at a gap between the forks 14 for rotably supporting the hub housing 181, such that power is generated by a coil 192 of the wheel shaft 182. If the tire 15 is rotated to drive the hub housing 181, the magnet 191 moves with respect to the power generation coil 192 to constitute the power generation effect. Although such hub power generator features a low resistance, an integral structure and a low failure rate, yet it still has the following shortcomings:
1. Uneasy Installation: Since the power generator is installed onto the hub, a larger sized hub is required, unless the power generator is built in the wheel at the time of assembling a new bike. If such power generator is installed afterward, it is necessary to replace the entire wheel, and thus makes the installation difficult.
2. Low Efficiency: The power generator generates electric power by using the axle center, and thus its rotation speed is equal to the wheel rotation speed of the bicycle, and is much less than the rotation speed of the dynamo powered lamp. Obviously, the efficiency will become very low. In order to achieve an output power equal to that of the dynamo powered lamp, a larger power generator is required.
3. Non-detachable Device: The power generator cannot be detached from the wheel when the power generator is not in use. Although the power generator has a low resistance when it bears no load, the power generator requires a very high efficiency to meet the high output requirement by a low rotation speed, and thus the gap between the magnet and the stator must be very small, and there is a resistance occurred and creating a burden to the rider when the power generator is not in use.
4. High Price: A larger power generator incurs a higher cost.
5. Exposure of Electric Wire: The lamp cannot be installed directly, and thus a section of electric wire is exposed in order to connect the lamp, so that the exposed electric wire may be pulled apart or deteriorated to cause a short circuit or a break of the electric wire.
Obviously, both of the aforementioned conventional way of generating power for a bicycle have drawbacks and required further improvements.